Acrylate is an extremely important basic raw material and intermediate in modern chemical industry, which is widely used in many applications such as adhesives, coatings, plastics, textiles, paper making, leather, elastomers, printing, synthetic fibers, building materials, superabsorbent resins, anti-scaling of boilers, UV/EB curing, flocculant, additive industry and detergent industry.
The wastewater discharged from the acrylate production device usually has the characteristics of high salt content, high organic matter concentration, high toxicity and difficulty in treatment, wherein the total dissolved solids (TDS) is up to 50-120 g/L, and the chemical oxygen demand (COD) is up to 30,000-90,000 mg/L. The main pollutants in the wastewater are sodium acrylate and catalysts of sodium salts which, depending on the catalyst, may be sodium p-toluenesulfonate, sodium methanesulfonate or sodium sulfate. Due to the high salt content, difficulty in treatment and that it is not suitable for incineration treatment, the treatment is mainly carried out by a biological treatment after significant dilution. However, the biological treatment system is low in load, large in area, and susceptible to impact, and the effluent water quality is unstable.
On the one hand, the acrylate wastewater has high concentration of pollutants, is difficult to handle and has high treatment cost; on the other hand, the wastewater contains high concentration of sodium acrylate, which has resource values. Therefore, how to convert the organic acid salts with high concentration in the wastewater into useful resources is the key for the treatment of acrylate wastewater.
At present, a number of patents have been proposed to utilize the acrylic acid in the wastewater from the acrylate devices to realize the resource utilization, such as production of modified lignosulfonate (CN103588935A), boiler scale inhibitor (CN103408175A), adsorption resin (CN103435737A), titanate adsorbent (CN103406091A), soaping agent (CN102206562A), dispersing agent (CN102225976A), and the like. Although the concentration of pollutants in acrylate wastewater is high, when it is used as a raw material to produce products, the total amount is relatively small, resulting in a small scale of production. Furthermore, it is required to establish a separate production device, which has high operation and maintenance costs, often has no economic value, and thus is difficult to apply in pollution control practices. Therefore, it is necessary to develop a process for utilizing the wastewater resource within the acrylate production process to reduce the concentration of pollutants discharged from the production process.